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Raman Spectroscopic (raman + spectroscopic)
Terms modified by Raman Spectroscopic Selected AbstractsDoping of C60 Fullerene Peapods with Lithium Vapor: Raman Spectroscopic and Spectroelectrochemical StudiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2008Martin Kalbá Abstract Raman spectroscopy and in situ Raman spectroelectrochemistry have been applied to the study of the lithium vapor doping of C60@SWCNTs (peapods; SWCNT=single-walled carbon nanotube). A strong degree of doping was proven by the disappearance of the radial breathing mode (RBM) of the SWCNTs and by the attenuation of the tangential (TG) band intensity by two orders of magnitude. The lithium doping causes a downshift of the Ag(2) mode of the intratubular C60 by 27,cm,1 and changes the resonance condition of the encapsulated fullerene. In contrast to potassium vapor doping, the strong downshift of the TG band was not observed for lithium doping. The peapods treated with lithium vapor remained partially doped even when they were exposed to humid air. This was reflected by a reduction in the intensity of the nanotube and the fullerene modes and by the change in the shape of the RBM band compared with that of the undoped sample. The Ag(2) mode of the intratubular fullerene was not resolved after contact of the lithium-doped sample with water. Lithium insertion into the interior of a peapod and its strong interaction with the intratubular fullerene is suggested to be responsible for the air-insensitive residual doping. This residual doping was confirmed by in situ spectroelectrochemical measurements. The TG band of the lithium-doped peapods did not undergo an upshift during the anodic doping, which points to the formation of a stable exohedral metallofullerene peapod. [source] The Intermediate Frequency Modes of Single- and Double-Walled Carbon Nanotubes: A Raman Spectroscopic and In Situ Raman Spectroelectrochemical StudyCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2006Martin Kalbac Dr. Abstract The intermediate frequency modes (IFM) of single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) were analyzed by Raman spectroscopy and in situ Raman spectroelectrochemistry. The inner and outer tubes of DWCNTs manifested themselves as distinct bands in the IFM region. This confirmed the diameter dependence of IFM frequencies. Furthermore, the analysis of inner tubes of DWCNTs allowed a more-precise assignment of the bands in the IFM region to features intrinsic for carbon nanotubes. Although the inner tubes in DWCNTs are assumed to be structurally perfect, the role of defects on IFM was discussed. The dependence of IFM on electrochemical charging was also studied. In situ spectroelectrochemical data provide a means to distinguish the bands of the outer and inner tubes. [source] Raman spectroscopic and X-ray investigation of stressed states in diamond-like carbon filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1-2 2005R. Krawietz Abstract The non-destructive characterization of intrinsic stress is very important to evaluate the reliability of devices based on diamond-like carbon (DLC) films. Whereas the only requirement for the X-ray diffraction method is a crystalline state of specimen, Raman spectroscopic stress analysis is restricted to materials showing intensive and sharp Raman peaks. On the other hand, Raman spectroscopy offers the possibility to measure stress profiles with lateral resolution of about 1 micron. The results of stress measurements in DLC films using both X-ray diffraction and Raman spectroscopy are found in very good correspondence. Mean stress in carbon films consisting of very small crystallites on silicon substrates has been determined by measuring and fitting the stress profiles in the substrate near artificial vertical film edges. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Valence-Tautomeric RbMnFe Prussian Blue Analogues: Composition and Time Stability InvestigationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2009Lionel Salmon Abstract Three different stoichiometric forms of RbxMn[Fe(CN)6]y·zH2O [x = 0.96, y = 0.98, z = 0.75 (1); x = 0.94, y = 0.88, z = 2.17 (2); x = 0.61, y = 0.86, z = 2.71 (3)] Prussian blue analogues were synthesized and investigated by magnetic, calorimetric, Raman spectroscopic, X-ray diffraction, and 57Fe Mössbauer spectroscopic methods. Compounds 1 and 2 show a hysteresis loop between the high-temperature (HT) FeIII(S = 1/2),CN,MnII(S = 5/2) and the low-temperature (LT) FeII(S = 0),CN,MnIII(S = 2) forms of 61 and 135 K width centered at 273 and 215 K, respectively, whereas the third compound remains in the HT phase down to 5 K. The splitting of the quadrupolar doublets in the 57Fe Mössbauer spectra reveal the electron-transfer-active centers. Refinement of the X-ray powder diffraction profiles shows that electron-transfer-active materials have the majority of the Rb ions on only one of the two possible interstitial sites, whereas nonelectron-transfer-active materials have the Rb ions equally distributed. Moreover, the stability of the compounds with time and following heat treatment is also discussed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Triplex Au,Ag,C Core,Shell Nanoparticles as a Novel Raman LabelADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Aiguo Shen Abstract Monodispersed, readily-grafted, and biocompatible surface-enhanced Raman spectroscopic (SERS) tagging materials are developed; they are composed of bimetallic Au@Ag nanoparticles (NPs) for optical enhancement, a reporter molecule for spectroscopic signature, and a carbon shell for protection and bioconjugation. A controllable and convenient hydrothermal synthetic route is presented to synthesize the layer-by-layer triplex Au,Ag,C core,shell NPs, which can incorporate the Raman-active label 4-mercapto benzoic acid (4-MBA). The obtained gold seed,silver coated particles can be coated further with a thickness-controlled carbon shell to form colloidal carbon-encapsulated Aucore/Agshell spheres with a monodisperse size distribution. Furthermore, these SERS-active spheres demonstrated interesting properties as a novel Raman tag for quantitative immunoassays. The results suggest such SERS tags can be used for multiplex and ultrasensitive detection of biomolecules as well as nontoxic, in vivo molecular imaging of animal or plant tissues. [source] Ambipolar Organic Field-Effect Transistors from Cross-Conjugated Aromatic Quaterthiophenes; Comparisons with Quinoidal Parent MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Rocío Ponce Ortiz Abstract This contribution presents an electrochemical, Raman spectroscopic, and theoretical study probing the differences in molecular and electronic structure of two quinoidal oligothiophenes (3,,4,-dibutyl-5,5,-bis(dicyanomethylene)-5,5,-dihydro-2,2,:5,,2,-terthiophene and 5,5,-bis(dicyanomethylene)-3-hexyl-2,5-dihydro-4,4,-dihexyl-2,2,,5,5,-tetrahydro-tetrathiophene) with terminal tetracyanomethylene functionalization and aromatic oligothiophenes where acceptor moieties are positioned at lateral positions along the conjugated chain (6,6,-dibutylsulfanyl-[2,2,-bi-[4-dicyanovinylene-4H-cyclopenta[2,1-b:3,4-b,]dithiophene]). In this way, the consequences of linear and cross conjugation are compared and contrasted. From this analysis, it is apparent that organic field-effect transistors fabricated with cross-conjugated tetrathiophene semiconductors should combine the benefits of an electron-donor aromatic chain with strongly electron-accepting tetracyanomethylene substituents. The corresponding organic field-effect transistors exhibit ambipolar transport with rather similar hole and electron mobilities. Moreover, n-channel conduction is enhanced to yield one of the highest electron mobilities found to date for this type of material. [source] Ultraviolet resonance Raman spectroscopy of locked single-stranded oligo(dA) reveals conformational implications of the locked ribose in LNAJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2009Stanislav O. Konorov Abstract We report here the first UV resonance Raman spectroscopic (UVRRS) study on locked nucleic acid (LNA) oligomers. Locking a base in nucleic acid (NA) oligomers produces a conformational change in the glycosyl bond between backbone and base. We present evidence of this change in LNAs when compared to their natural analogs using UVRRS. Wavenumber downshifts and peak amplitude increases, especially of the ,1481 cm,1 peak that is a spectral marker for part of the glycosyl bond, correlate with the fraction of locked bases when single-stranded oligomers incorporating up to three locked bases were examined. By varying the position of the locked base within a fixed length sequence, we conclude that one, or at most two bases, on either side of the lock is affected. We further conclude from these data, and previously published reports, that the conformation of LNA is determined by imidazole,imidazole and pyrimidine,pyrimidine repulsion and imidazole,pyrimidine attraction in contrast to dispersion attraction-dependent aggregation in the B conformation of DNA. Copyright © 2009 John Wiley & Sons, Ltd. [source] Synthesis of hafnium tungstate by a CO2 laser and its microstructure and Raman spectroscopic studyJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2008E. J. Liang Abstract Densely packed hafnium tungstate blocks were synthesized by rapid solidification with a CO2 laser. It is shown that the optimum synthesis conditions for HfW2O8 are around 700 W laser power and 1 mm/s scan speed. Scanning electron microscopy (SEM) observation shows that the blocks consist of oriented nano-threads/rods that grew horizontally on the surface region and vertically in the interior. The orientations of the nanostructures are governed by the heat transfer directions on the surface and in the interior. Raman spectroscopic and X-ray diffraction studies show that the samples solidified in the cubic structure with minor contents of the orthorhombic phase. This is explained by a compressive stress induced during the rapid solidification process due to a sudden drop of temperature of the molten pool to the ambient. The stress is estimated to be about 0.6 GPa by comparison with high-pressure Raman study. Some specific Raman bands appear in the samples synthesized with the laser synthetic route but not in the sample by solid-state reaction. Copyright © 2008 John Wiley & Sons, Ltd. [source] A Raman spectroscopic and combined analytical approach to the restoration of severely damaged frescoes: the Palomino projectJOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2008Howell G. M. Edwards Abstract The deterioration of art objects is normally relatively minor, controllable and attributable to environmental changes or bacterial invasion, and until now there has not been any recorded attempt to analyse an artwork that has been deliberately and significantly destroyed. The analytical problems are correspondingly larger but the potential reward from any information that can be forthcoming is thereby proportionately greater. The 17th Century Palomino frescoes on the vaulted ceiling of the Church of Sant Joan del Mercat in Valencia were largely destroyed by insurgents in the Spanish Civil War in 1936. The ensuing gunfire and a series of seven conflagrations inside the church had a devastating effect upon the artwork, and the surviving areas were also rendered unstable with respect to their detachment from the substrate. During the current restoration project being undertaken on these frescoes, an opportunity was provided for the application of several analytical techniques to secure information about the original pigment palette employed, the technology of application used by Palomino and the changes consequent upon the destruction process. Here, we report for the first time the use of analytical Raman spectroscopy, supported by scanning electron microscopy (SEM) and voltammetry of microparticles, for the combined identification of pigments, binders, substrate treatments and pigment alteration in an important, although badly damaged, wall painting for the informing of the ongoing conservation and restoration strategy. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||